Explained in Depth: The Past, Present and Future of Mobile Ad hoc Networks

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Mobile ad hoc networks (MANETs) have come a long way from their origins in packet radio networks in the 1970s. Let‘s trace the fascinating evolution of this decentralized form of wireless networking and get a deeper look at how MANETs work, their applications, challenges, and emerging innovations.

Demystifying the Technology Behind MANETs

MANETs enable robust wireless networking in the absence of fixed infrastructure through the clever use of dynamic routing protocols. But how do these algorithms actually work to set up and maintain connections as nodes move around?

Popular proactive protocols like Optimized Link State Routing (OLSR) periodically flood the network with control messages so each node can build a complete map of the network topology. This enables efficient routing but consumes more bandwidth.

Reactive protocols like Ad-hoc On-Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) instead discover routes only when needed. AODV uses sequence numbers to ensure loop-free forwarding while DSR uses source routing, storing complete paths in the packet headers.

Researchers are now looking at innovative hybrids like Zonal Routing Protocol (ZRP) which combines proactive and reactive approaches based on zone radii. Simulations have shown ZRP to have up to 35% lower latency compared to pure reactive routing!

![Routing protocols](protocols.png)
*A comparison of common MANET routing protocols and their key characteristics.*

Protocols also use clever tricks like hierarchical approaches, fuzzy logic, and swarm intelligence to improve efficiency, security and adaptability. But many open challenges remain in areas like cross-layer optimization, scalability and quality of service provisioning.

The Growing Importance of MANETs for Next-Gen Applications

While MANET research started in academia and the military, it is now finding many practical civilian applications as wireless devices get more powerful and ubiquitous.

In fact, MarketsAndMarkets predicts the global MANET market to grow from $10.2 billion in 2017 to over $25 billion by 2022! Key growth drivers include:

  • Expanding adoption in warehousing, manufacturing, and industrial IoT with projections of over 30 billion connected devices by 2023. MANETs are ideal for machine-to-machine communication.

  • Growing use in commercial drones and autonomous vehicle networks. Complex emergent behavior can be realized through dynamic MANET-style connectivity.

  • Use in smart cities, especially for public safety and intelligent transport systems. Vehicles can form VANETs – a type of MANET for collision avoidance and traffic updates.

  • Surging demand in healthcare services from remote patient monitoring to telemedicine and ambulance networks. This is driving innovation in QoS for better support of bandwidth-intensive apps.

![Market growth](growth.png)

The global MANET market is projected to grow at a CAGR of 14% till 2022. IoT and transport are key growth sectors.

Evolution in artificial intelligence and machine learning is also unlocking new use cases. By adopting a cognitive networking approach, nodes can intelligently adapt transmit power, modulation schemes, and routing based on traffic conditions and application requirements.

Overcoming Key Challenges for Next-Gen MANETs

Despite promising new applications, MANET research continues to face challenges in flexibility, scalability, security and energy efficiency.

Mobility management remains difficult, especially with increasingly complex autonomous and aerial vehicles. Handoff delays as UAVs move between base stations can degrade performance. More intelligent predictive handoff and route maintenance mechanisms are required.

Expanding scale also threatens network performance due to interference, overhead of control traffic, and sub-optimal resource allocation. Studies have found network throughput in 50 node MANETs to drop by over 60% compared to 10 nodes. Hierarchical architectures and clustering offer a potential solution.

Security is another critical challenge. The dynamic topology and lack of centralized control leaves MANETs exposed to jamming, spoofing, eavesdropping, and denial-of-service attacks. Promising directions include decentralized trust management, authentication, incentive mechanisms, and machine learning for anomaly detection.

Battery technology is not keeping pace with processing and communication capabilities. Innovative energy harvesting techniques like solar, kinetic, and RF along with optimized signaling can help overcome the power bottleneck. Cross-layer designs that jointly consider factors from physical to application layers show up to 2x improvements in energy efficiency.

The Road Ahead: MANETs to Evolve Towards AI and 6G

MANET research has come a long way but the next decade promises to be even more transformative with several key trends:

  • Proliferation of IoT and smart devices will drive large-scale dense MANET deployments across industrial, vehicular, and smart city ecosystems. This will require rethinking protocols, architectures, and spectrum access.

  • Evolution towards cognitive networks with nodes seamlessly sharing resources and spectrum as needed. Look forward to context-aware, goal-oriented, self-organizing systems.

  • Integration with cloud and edge computing to enable advanced functionality and performance akin to centralized systems. Computing on resource-rich cloud servers or edge nodes can overcome device constraints.

  • Leveraging AI and machine learning for more intelligent, predictive and adaptive protocols and networking. ML has the potential to revolutionize areas from routing, scheduling, and security to hardware design.

  • Incorporating new 6G breakthroughs like terahertz bands, 3D networking, and nanoscale communications. 6G-enabled MANETs will unlock exciting applications from truly immersive VR to medical nanobots.

The dynamic nature and decentralized flexibility of MANETs will ensure they continue to evolve and find new applications. It is an exciting time to be exploring this cutting-edge field of wireless networking research!

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